Definitely eskate. I've had a boosted v2 for six years and it's awesome, but the options out there now from backfire and meepo are insane step ups in speed and battery life, for the same money or less.

I love it especially as a last mile option in conjunction with buses and trains.

Electric longboard maybe?

That seems like the best option. Adding a motor to a longboard is just enhancing a known proven quantity. It won't have the maneuverability of a onewheel or the all-terrain ability, but longboards are definitely a proven vehicle for roadways so motorized ones seem fine.

That or kickscooters, but they're not as compact as the onewheel or a longboard.

Fundamentally, the onewheel seems like a personal-mobility answer to the V22 Osprey: a vehicle with amazing functionality and versatility in its happy path, but is fundamentally unsafe in failure because of the basic physics of the situation.

edit: onewheel, not longboard, in the final paragraph.

Small skateboard with big soft wheels. 6-7lbs or so. Can shove it between your legs on the train.

Electric unicycles win this category for fun, compact, motorized transportation, tho there's more of a learning curve than scooters or bikes.